The application of treatment agents to a textile web is commonly achieved in one of two manners, one being immersing the textile web into a bath of the treatment agent so that the dye soaks into the textile web and the second being applying treatment agent (which may be a liquid or a particulate treatment agent) to one or both faces of the textile web. Immersion (also commonly referred to as a dip-coating process) of the textile web requires a substantial amount of treatment solution to be used to saturate the textile web. In addition, following saturation the textile web must be washed to remove a substantial amount of unbound treatment agent from the web. While dip-coating results in good penetration of the treatment agent throughout the entire textile web, it presents a relatively inefficient use of the treatment solution and requires considerable post-processing of the web.
Treatment agent may instead be applied (such as by spraying or coating) to one or both faces of the textile web by any number of application techniques including, without limitation, ink jet systems, spray systems, gravure roll, slot die, rod coater, rotary screen curtain coater, air knife, brush and the like. Following the application of a treatment agent to the web, the web is often heated and/or steamed to promote binding of the treatment agent to the textile web. The textile web is then washed, such as in a bath of water or other cleaning solution, to remove unbound and excess treatment agent from the web.
Applying a treatment agent to the textile web in this manner (e.g., as opposed to dip-coating) requires considerably less treatment agent to be initially applied to the web, and thus reduces the time spent heating/steaming the web to facilitate binding of the treatment agent to the web, and also reduces the amount of unbound treatment agent that needs to be subsequently washed from the web. Such treatment operations where the agent is applied to only one face of the textile generally use less treatment agent, but run the associated risk that the treatment agent does not adequately penetrate into and through the web to the opposite face to provide even or uniform treatment of the web. While applying treatment agent to both faces of the textile web somewhat reduces this risk it also requires additional treatment agent to be used, resulting in more unbound treatment agent that must be subsequently removed from the web.
In particular applications, such as where the web is to be used as a filter medium, it is known to apply (e.g., by printing) one or more treatment agents to the surface, or face of the web to impart specific properties or characteristics to the filter medium, such as odor control, anti-microbial, and the like. The treatment agent is simply allowed to wick into the web without much uniformity. As a result, the desired characteristic is non-uniformly present in the web. Where more than one treatment agent is desired, it is difficult to apply a second treatment agent without coating or otherwise inhibiting the first treatment agent.
There is a need, therefore, for a process that reduces the amount of treatment agent that needs to be used in treating a textile web and facilitates improved penetration of one or more treatment agents into and through the web.